When I got hired as a SQL Developer with little experience. I got a rundown on my employers database and tables and then tried my best. Google and Stack was the best teacher and with each work assignment I learned something new or a better way to do what I did before. Often the SQL queries I wrote would require updates and I would put in better solutions.
There’s still a ton of stuff I don’t know and I made a lot of mistakes along the way , but I still feel like this was the best learning experience for me.